Transmission Fluid Change

[mikeharriswho]

I've heard stories about changing transmission fluid on high mileage cars. Some saying not to do it because it will cause problems, others saying the problems were already there and new fluid never hurts. My Accord is approaching 342,000. I just got it and Im in the process of getting it in top shape, which it wasn't far from it. Should I change the fluid? What do ya'll think? If I should, what fluid do you guys recommend. It is a 5speed by the way.

[g.frost]

The manual calls for changing manual transmission oil every 30K miles, that is a good idea. There is not a good reason to let it go much longer than this; 50K max for synthetic. Don't use motor oil either, current oils are not a good match. Honda MTF used to be a good alternative but current versions of this fluid are getting too thin (6 vs. 10cst). I use Red Line MTL in all Honda manual transmissions with excellent results. Heard good things about GM synchromesh as well.
Be sure to take the fill bolt off before draining the fluid so you are sure to get it filled... it can be a tough nut to crack.

[MessyHonda]

I been loyal to Honda MTF but regular 10w-30 oil works. Our transmissions do no like synthetic oils. I replaced mine with 5w-30 semi synthetic and my transmission got stock in 5th gear because I overheated the synchros. I had to get my 140k mile transmission rebuilt. Gm synchromesh works good from what other members told me. Its also a good idea to upgrade to 88 civic polyurethane bushings to make the shifts more precise.

[g.frost]

Don't use synthetic motor oils. Modern motor oils do not have a proper add pack for transmission oil.
Most issues you hear about are loosing 5th gear in these transmissions. It is on top of the gearbox and likely has oil starvation issues. Be sure to always keep the gearbox full as lower levels will give 5th even less oil.

Honda is now on rev 3 of MTF. They keep getting thinner and always shear even thinner within 15-25K miles.
Current rev will be below 6cst, within a few k miles. (....for better gas mileage) I think that is too thin for the 3g.

I started using Redline MTL in '87 Civic. It went 380K miles, never opened the transmission.
My 88 DX is at 167K, shifts and works same as new. MTL since 30k miles.
05 Civic is close to 150K, was notchy 1-2nd since new. Waited to 3.5k miles, no improvement. Switched to MTL, very nice & smooth ever since. There is not a better manual transmission lube for these. Change at 30-40k miles.
MTL is 10cst. Unless you live in a very cold climate, I would not go much thinner.
If you want to look up more data on MTL and MTF, try Bobistheoilguy.